Show/hide don't trigger when the popovers are actually shown and hidden

[hworld]

Made a PR to address this: #117
Note that it is a breaking change. I wasn't sure the best way to address it.

The problem is that there is no way to actually know when the popover is visible on screen. There are possibilities to delay the show or hide, as well as not having it hide on hover of the popover itself. Since the emitting of show and hide happened as soon as hide() and show() were called, but not when the actual show/hide logic ran, it was impossible to really know if it was being shown or not.

I'm not sure if there needs to be work done with the update:open emitter. If the goal is to sync the "open" prop, then it seems like it won't actually work since the isOpen variable changes elsewhere.